Author Topic: Anyone Had 12v Issues?  (Read 1687 times)

Kremmen

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Re: Anyone Had 12v Issues?
« Reply #15 on: January 21, 2025, 03:54:28 AM »
All cars are started by an electric motor  :'(

In the MK4 case it's the HV battery not the 12v battery

Got to love some dealers training
Let's be careful out there !

5thcivic

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Re: Anyone Had 12v Issues?
« Reply #16 on: January 21, 2025, 02:11:41 PM »
The point is about the voltage needed to boot the regulators powering the microprocessors and thus enable the HV relays to be connected to and control the motor. If the car does start on 10V that is interesting information.

John Ratsey

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Re: Anyone Had 12v Issues?
« Reply #17 on: January 21, 2025, 06:08:56 PM »
The point is about the voltage needed to boot the regulators powering the microprocessors and thus enable the HV relays to be connected to and control the motor. If the car does start on 10V that is interesting information.
I find the 10V threshold implausible. I had an interesting experience with my HR-V after it had been standing for the better part of two months. The car unlocked as usual, the power button worked but the dashboard then filled with warning symbols and error messages telling me that numerous features weren't working. The screen in the middle of the dashboard didn't power up and I concluded that there wasn't enough life in the battery to close the contactor to connect the HV battery. There was no other indication that the 12V battery was low.

IIRC the 12V battery measured over 12V on my volt meter. I connected my smart charger which, after less than a minute claimed the battery was fully charged (which it obviously wasn't). Fortunately I had an old dumb charger which pushed some juice into the battery after which everything was OK and the vehicle started normally. It's possible that the 12V battery isn't in the best of health as two years ago it had a dose of the HR-V's flat battery problem (when a software bug randomly didn't power down everything when the doors were locked).
2022 HR-V Elegance, previously 2020 Jazz Crosstar

5thcivic

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Re: Anyone Had 12v Issues?
« Reply #18 on: January 21, 2025, 08:51:19 PM »
That sounds like a battery that can show 12v on a voltmeter which requires no current, and a smart charger, display likewise, but cannot supply several amps to fire up the electronics and displays without being charged with some power first.
I am slightly surprised by the 10V figure, but it is perfectly possible for a good battery as plenty to spare to regulate 5V supplies for the electronics and any step up regulators for displays etc.

Botak

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Re: Anyone Had 12v Issues?
« Reply #19 on: January 22, 2025, 08:15:29 AM »
May be it is usefull to add a part of the text of an old post of mine regarding the 12v battery during long time stand still:
.........to share our last experience with a long stand still during winter (every time about 2 and a half months). I have already shared the data of the battery-charge of our Jazz in the first 2 years. I can add the figures of this year. For clarity, I give the data of the 3 years together:
2022: departure 12,8V return: 11,9V
2023: departure 12,6 V return:11,6V
2024: departure 12,5V return: 11,7V
Even considering the soft Dutch winters (certainly in a garage), the small 12V battery is quite sturdy. The charge of the battery is deteriorating, but very slowly. And did I first wonder if the battery could cope with one long standstill of 2 and a half months (and was already searching for a fitting EFB-battery for replacement) now my only concern is that I can get exactly the same battery when I have to change the battery in a couple of years......
In two month time I could add the figures of 2025, but I will only mention it when the battery this time says that I have asked too much and that I have to use a charger or I have to replace it. So no news is good news

Lord Voltermore

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Re: Anyone Had 12v Issues?
« Reply #20 on: January 22, 2025, 10:44:54 AM »
When my current car  (excuse pun)  goes through periods of little use the battery might show less than 12v. Its less than  4 months old.   

I started it this morning.  Initially it showed 12.0V  dropping to 11.7 / 11.6 volts for about a second whilst the computer did its checks, rising to 14.4 charging  voltage  when the ICE started. (It also continues to receive  14.4 volt when in EV mode with the ICE off)

  It was last used a week ago for about 4 miles, parked for a few hours then same journey home. And has only had similar pattern of little use since its last long trip in December.  (long trips  planned soon)   
 
With my previous mk 4 my main concern was that the accepted wisdom for 12v lead acid batteries is that 12v or less means its flat  and liable to irreversible cell damage.   But it was  sometimes  under 12v when little used.  Periodically using a mains trickle charger is probably a good idea but I was too lazy to ever put an extension lead out to the driveway  :-[ . And I only ever used a solar charger once, early on.   Despite this the car never failed to start  in 3 years of  ownership. .

My understanding is the computer does some initial checks .If these are correct it then throws a heavy duty solenoid to connect the high voltage battery which then starts the ICE.  I can accept that 10 Volts  may be enough for these functions.   If there is not enough  power left in the '12v' battery  to  throw the solenoid the ICE wont be able to start but there may be warning lights. But  some external charging or a momentary boost from a battery pack jump starter should be enough for the HV battery to connect and take over. 

 
Master of brevity and self delusion
 

CtrlAltDel

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Re: Anyone Had 12v Issues?
« Reply #21 on: January 22, 2025, 11:05:33 AM »
I’m not so sure, I think my 12v gave up on me this morning. Its now with the dealer to check

ninanina

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Re: Anyone Had 12v Issues?
« Reply #22 on: January 22, 2025, 03:21:16 PM »
I’m not so sure, I think my 12v gave up on me this morning. Its now with the dealer to check

As your Jazz is 4 years old, and possibly the 12v battery a bit older, it’s probably a bad battery

Please let us know what the dealer says

CtrlAltDel

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Re: Anyone Had 12v Issues?
« Reply #23 on: January 22, 2025, 03:29:15 PM »
I do hope that’s all it is tbh!

ninanina

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Re: Anyone Had 12v Issues?
« Reply #24 on: January 23, 2025, 01:03:57 PM »
I do hope that’s all it is tbh!

What was the outcome?

CtrlAltDel

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Re: Anyone Had 12v Issues?
« Reply #25 on: January 23, 2025, 03:51:58 PM »
Just found out battery needed replaced.  There is another fault however so they are trying to replicate it and I’ve left the car with them.

ninanina

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Re: Anyone Had 12v Issues?
« Reply #26 on: January 23, 2025, 05:58:53 PM »
Just found out battery needed replaced.  There is another fault however so they are trying to replicate it and I’ve left the car with them.

Well at least they found the 12v battery needed replacing

Can I ask what the other fault is?

CtrlAltDel

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Re: Anyone Had 12v Issues?
« Reply #27 on: January 24, 2025, 04:17:19 PM »
Turtle icon with unexplained low and high temps appearing - dealer thinks it needs a cable replacing (god knows) but we need the turtle to reappear to get the code. 😭

Geoff_W

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Re: Anyone Had 12v Issues?
« Reply #28 on: February 02, 2025, 05:20:23 PM »
I had been in Australia over Christmas and the New Year. Arrived back home on January 6th to sub zero temperatures. The next morning my 2021 Jazz Crosstar wouldn't start. Doors unlocked but wing mirrors didn't fully open. Pressing the Start button resulted in no engine start and an error message on the driver's display saying that there was a fault on the auto braking system. Called Honda Breakdown who called out the AA. Because it wasn't a priority (fair enough) they didn't arrive until after dark. It was snowing heavily, but the AA guy was very good and diagnosed a dead battery. He got the car started with a power pack and then attached his diagnostic tablet to the service port. The upshot was a new (Bosch) battery with a 5yr warranty which cost me £135. Car has been fine since.

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